Connector assembly

ABSTRACT

An electrical receptacle having a power energized safety-lock to prevent insertion, or withdrawal, of a second component such as a receptacle cover, or a plug for connection therewith, while the receptacle is energized. Energy for urging a plug-engaging finger into a lock position in which it can obstruct the movement of the plug in or out of the receptacle is provided by a strong spring. However, only a small amount of energy is required to maintain, or lock the plug-engaging finger in this lock position when, as in accordance with this invention, a boltlike obstruction is moved to block the release-motion of the plug-engaging finger. The bolt is moved to its lock position by a solenoid which is energized in parallel with the receptacle contacts.

O United States Patent 1 3,569,908

[72] Inventor Arthur I. Appleton 3,350,675 10/1967 Misencik etal 339/121 Bndkwood Road Nonhbmok 60062 Primary Examiner-Marvin A. Champion ag fiAssistant Examiner-Joseph H. McGlynn V d 45 Patented Mar. 9, 1971 9999993!! [54] CONNECTOR ASSEMBLY A BSTRACT: An electrical receptaclehaving a 5556555 6CIaims8Drawing figs. gized safety-lock to preventinsertion, or withdrawal, of a second component such as a receptaclecover, or a plug for [52] U.S. Cl. 339/91, connection therewith whilethe receptacle is energized Ener. 335/170 339/111 gy for urging aplug-engaging finger into a lock position in [51] Ill. Cl- H011 13/54 hih it can b t t th movement f th l i or t fth [50] Field of 339/12, 45,receptacle is provided by a Strong spring. However only a 91, 111;335/168, 170, 171; 317/( q small amount of energy is required tomaintain, or lock, the r plug-engaging finger in this lock positionwhen, as in ac- [56] References cued cordance with this invention, aboltlike obstruction is moved 1 UNlTED STATES PATENTS to block therelease-motion of the plug-engaging finger. The 1,082,032 12/1913 Levin339/91 bolt is moved to its lock position by a solenoid which is ener-2,874,336 2/1959 Wannemacker 317/1 1 gized in parallel with thereceptacle contacts.

42 $7 46 I 4 ,g.; f0 6'] 11 ,2 J] 6! a7 11! 12 J6 l i v i 64! w Lli m j!22 ii 2 l].4,9 I. t L -u EL CONNECTOR ASSEMBLY BACKGROUND or THEINVENTION This invention relates to electrical connectors designed foruse in areas classified as hazardous because of the presence ofcombustible vapor, gas, dust, or other ignitible material.

The electrical arc which may occur when a plug is inserted into orwithdrawn from an energized receptacle may cause injury to personneldirectly, and may cause an explosion in a hazardous area. Also, exposedenergized electrical contacts may cause personnel injury from electricalshock. In the past these problems have been countered mainly by variousingenious devices which confine the are or which deenergize the exposedelectrical contacts whenever insertion is not complete.

SUMMARY OF THE INVENTION The present invention relates to a lockingmechanism for electrical plugs which will prevent separation of the plugand receptacle or connector body when electrical energy is present,which employs a relatively low power solenoid to achieve locking andwhich is positive in operation.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway, partiallycross-sectional view of a connected plug and receptacle utilizing theprinciples of this invention.

FIG. 2 isa planview of the receptacle utilizing the principles of thisinvention showing the receptacle closed by a lockable cap. I

FIG. 3 a view from the end of the open receptacle taken approximatelyalong the line 3-3 of FIG. 2.

FIG. {Us a partially cross-sectional view taken along the line 4-4 ofFIG. 2. 1

FIG. Sjis an enlarged cross-sectional view showing the relativepositionof the plug and receptacle at four stages of insertion of theplugint'o, the receptacle.

FIG. 61 a; greatly enlarged cross-sectional view showing detailsofvarioiiselements visible in FIGS. 1 and 5.

FIG. 7 is a fragmentary plan view of a plug with suggested positionsiofthe plug-engaging components of the receptacle which illustrates analternative construction of a preferred embodiment of this invention.

FIG. 8 is an exploded detailed perspective view of plug-engaging meansin accordance with a preferred embodiment of this invention.

DESCRIPTION OF PREFERRED EMBODIMENT Although the followingdisclosure'offered for public dissemination in return for the grant of apatent is detailed to ensure adequacy and aid understanding, this is notintended to prejudice that purpose of a patent which is to cover eachnew inventive concept therein no matter how others may later disguise itby variations in form or additions or further improvements. The claimsat the end hereof are intended as the chief aid toward this purpose; asit is these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.

In accordance with preferred. embodiments of this invention, pluggenerally 10 or 10 is provided with grooves 11 and II in a cylindricalterminal portion or collar 12 thereof. At the sides of the grooves 11,the cylindrical portion forms abutments for locking engagement with alocking finger or detent 60, subsequently described. Terminal portion 12is adapted for insertion into receptacle generally 15, and polarizationkey 16 in receptacle (FIG. 3) requires proper orientation of the plug inthe receptacle. Upon complete insertion of plug 10 into receptacle l5,receptacle-contacts 18 are mated with plug contacts I9, whereby cable 20is energized through receptaole-inlet leads 21. Insulating shields 22partially protect receptacle-contacts I8.

It is conventional to employ a control circuit which preventsenergization ofthe receptacle leads until after control circuitcomponents, located in theplug, are engaged with control circuit leadswhich are located in the receptacle. Thus, while it is not essential toemploy such a safety measure in accordance with this invention, it isnaturally preferable to provide all possible protection against arcing.Thus, it is preferable to use the improvement of this invention inconjunction with the secondary safety measure, i.e. with theconventional control circuitry which prevents energization of the plugprior to connection of control circuit components in the plug andreceptacle. Thus plug contact 25 from the control circuits engagereceptacle control contacts 26 in the receptacle after engagement ofmain electrical contacts 19 and 18. This is perhaps best illustrated inFIG. 5 in which the relative position of plug cylinder 12, plugelectrical contact 19 and plug control circuit contact 25 are shown infour consecutive stages of insertion of plug 10 into receptacle 15. Thefour relative positions are in each case denoted A, B, C, and D. Thus,the position of main electrical contact 19 and control circuit contact25 designated A is the relative position of these components when thecylindrical portion 12 of plug 10 is in the position designated A. Thepositions marked B for main electrical contact 19 and control circuitcontact 25 are the relative positions of these elements when the end ofcylindrical portion 12 of the plug is inserted to the position marked B,etc. Plug control circuit contact 25 is not engaged with its respectivereceptacle control contact 26 when the plug is inserted to the positionindicated as C, at which point main electrical contact 19 is inengagement with receptacle contact 18 in the position indicated as C.

It is emphasized that the control elements" 25, and 26 are not directlyrelated to the operation or control of the improvement of thisinvention, but rather, these elements are conventional componentsrelating to a secondary safety system.

In accordance with this invention a solenoid 30 is energized in parallelwith receptacle contacts 18 through leads 3] which are connected toreceptacle input wires 21. In accordance with one embodiment of thisinvention grooves ll extend around the complete circumference of theterminal cylindrical portion 12 of plug 10. Also, in one preferredembodiment of this invention a pair of solenoids generally 30, 30' areutilized on opposite sides of the receptacle 15.

In a more preferred embodiment of this invention, plug 10' is providedwith a large number of circumferential grooves thereon and receptacle15' is provided with a pair of solenoids and a pair of locking fingermechanisms which are not positioned directly opposite each other, butwhich are positioned so that one of the locking fingers strikes the plugbefore the other. This is best illustrated in FIG. 7 which shows therelative positions of the locking fingers as two stages of insertion ofa plug 10 into receptacle 15'. These stages are indicated as E and F,with E and E being the relative position of fingers at the indicatedstage of insertion and F and F the relative position of the fingers uponcomplete insertion of the plug 10 into receptacle 15. p

The locking mechanism of this invention includes solenoid coil 34,armature 35, shaft 36 and locking bolt 37. Coil 34 is secured to thereceptacle by means of a screw 39 which fixes coil frame member 40 toplate 41. Plate 41 is seated on shoul ders 42 and secured thereon byaccess plug 43. Armature 35 is secured to shaft 36 by pin 38. Shaft 36is supported by suitable bearing means 46. Spring 47 positioned betweencompression fit collar 48 and bearing means 46 urges shaft 36 in adirection which would withdraw armature 35 out of coil 34 to the approximate position shown in FIGS. 1 and 5. Spring 50 bears againstinward portion 57 of lock bolt 37 and against C-washer 51. C-washer 51is secured to link shaft 36 by reason of being seated in a notch (notseen) near the end of shaft 36. Link shaft 36 passes slideably throughthe opening in the inward portion 57 of lock bolt 37. Motion of bolt 37on shaft 36 is thus limited to the extent of compression available tospring 50, and is limited in the other direction by compression fitcollar 58. In FIG. 5 bolt 37 is shown positioned against collar 58 inits normal rest position. FIG. 6 however shows the relative positions ofcollar 58 and bolt 37 which are obtained when solenoid 30 is energizedwhile detent generally 60 is in the retracted position illustrated inFIG. 6.

The details of the associated structures and of the mounting of detent60 is perhaps best seen in the exploded view (FIG. 8). The detent 60comprises an arm portion 62, a groove-engaging portion or catch 61, andis provided with a hole 63 through which axle pin 64 passes. Thus detent60 is pivotally secured to mounting block 65 by passing axle pin 64through hole 66 in mounting block 65, then through hole 63 in fingermechanism 60 and finally through hole 66' in mounting block 65. Thissubassembly consisting of mounting block 65, axle pin 64 and lockingfinger mechanism 60 is positioned in the cavity 69 prior to installationof link shaft 36, in such position that the catch 61 passes through hole70 in inner wall 71 of the receptacle 15. Plate 75 having holes 76 andspring-tongue 77 with its downwardly rounded end portion 78 ispositioned on top of mounting block 65; and these units are secured toreceptacle 15 by bolts 79 and 79 passing through holes 76 and 76. Thedownwardly rounded portion 78 of spring-tongue 77 bears firmly againstthe opposed surface 67 of arm 62 of detent 60. Thus when detent 60 isretracted into the receptacle wall, in the position illustrated in FIG.6, spring-tongue 77 urges the finger mechanism in the direction shown inthat FIG. by the arrow, i.e. in the direction towards the plug.

The safety locking mechanism heretofore described is also useful tosecure a cover in place over the receptacle while the receptacle isenergized. Thus receptacle cover 80 is pivotally secured to receptacle15 by suitable hinge means 81. Means for receiving catch 61 is providedin U-shaped bracket 83 secured to cover 80 by bolts 84. Arms 85 ofbracket 83 carry recesses 86 for receiving catch 61. Thus cover 80, whenclosed as illustrated by full lines in FIG. 2, is held securely in placewhenever the receptacle is energized due to the fact that catch 61engages recesses 86 preventing the withdrawal of bracket 83 along innerwall 71 of receptacle l and bolt 37 blocks the pivoting path of detent60.

OPERATION When receptacle is not energized plug 10 may be insertedtherein. Various stages of insertion of the plug are illustrated in FIG.5. The position indicated by the letter A represents the stage ofinsertion at which catch 61 first contacts cylindrical portion 12 ofplug 10. At this stage of insertion main electrical contact 19 andcontrol contact are in the relative positions indicated at A. Continuedinsertion of the plug causes catch 61 to bear against beveled endportion 13 of plug 10 thus urging detent 60 to pivot in around pin 64out of abutment with end 13. This permits continued insertion of plug 10until catch 61 seats in the first circumferential notch indicated as1117 under the urging of spring 77.

At this stage of insertion catch 61 is inserted at the positionindicated at B and main electrical contact 19 and control circuitcontact 25 are in the relative positions indicated by the letter B inthe dotted outline of those elements. Thus at this stage of theinsertion, main plug electrical contact 19 is still spaced apart frommain electrical contact 18 in the receptacle.

Had the receptacle become energized while plug 10 was being insertedbetween the positions indicated at A and B in FIG. 5 the relativepositions of all the parts would be substantially that illustrated inFIG. 6. Thus locking finger 61 would have been pivoted into receptacle15. (Prior to energization, armature 35, link shaft 36 and locking bolt37 are in the position illustrated in FIG. 5.) If the receptacle isenergized at the stage of insertion described immediately above,connecting wires 31 attached to main receptacle input wires 21 inparallel with receptacle contacts 18 causes solenoid to be energized.This causes armature to be drawn into coil 34 to the approximateposition illustrated in FIG: 6. Thus shaft 36 moves with the armature,i.e. to the right in FIG. 6; whereupon movement of bolt 37 is obstructedby locking finger mechanism 60. Nonetheless, shaft 36 continues itsmotion, permitting armature 35 to be completely and properly drawn intocoil 34, because of the play provided in the slideable attachment ofbolt 37 to shaft 36. Upon the insertion of plug 10 to the positionindicated as B in FIG. 5. spring 77 urges detent 60 toward plug 10 sothat groove engaging portion 61 is urged in the direction of the arrowin FIG. 6 to reside in groove 11b. Thus spring 77 forces locking detent60 out of the path of bolt 37. As soon as locking finger mechanism 60 ispivoted downwardly out of the path of bolt 37, compression of lightspring 50 moves bolt 37 along the path indicated by the dotted lines inFIG. 6 in the direction of the horizontal arrow until it abutspositioning collar 58. Thus it is apparent that in this latterconfiguration detent 60 is no longer able to pivot into receptacle 15out of the path of plug 10 and catch 61 obstructs movement of plug 10 ineither direction as long as bolt 37 is in this lock position. (Theconfiguration in FIG. 4 illustrates the relative position of detent 60and locking bolt 37 when receptacle 15 is energized and cover is lockedin closed position. The same result will occur when plug 10 is insertedand locking finger 60 is in one of the grooves 11 with solenoid 30energized.)

Continued insertion of the plug when receptacle 15 is not energizedpermits plug contact 19 to engage receptacle contact 18 in the relativepositions indicated as C in FIG. 5. At this stage locking finger 61 candwell in circumferential groove in plug 10. Continued insertion to therelative positions indicated as D in FIG. 5 at which stage of insertionplug contact 19 is fully mated with receptacle contact 18 and controlcircuit plug contact 25 is mated with receptacle controi circuit contact26. Should plug 10 be inserted into receptacle 15 to a positionsomewhere between C and D, then the unlocked conditions again prevail.However, when the plug is inserted to a position between C and Dillustrated in FIG. 5 by the dashed lines, withdrawal of plug 10 fromreceptacle 15 is possible until the plug is withdrawn to the pointindicated by position C of the dashed lines.

It is noted that in the double safety combination illustrated in FIG. 5in which a separate safety device, namely the control circuit isemployed, control circuit contact 25 will have been separated from itsreceptacle contact 26 prior to reaching the position indicated as C inFIG. 5, thus causing the receptacle to be deenergized while mainelectrical contact 19 is still inserted in its receptacle contact 18.Thus, employment of the secondary safety circuit deenergizing thecontacts would prevent separation of the plug contact from thereceptacle contact while the receptacle contacts are energized. However,in those embodiments in which a safety control circuit is not employed,or in the eventuality that the safety control circuit is employed andmalfunctions, the combination of this invention would prevent separationof plug contact 19 from receptacle contact 18 by causing the plug to belocked-in at position C when catch 61 seats in groove lie with lockingbolt 37 sliding behind it to prevent locking finger 61 from beingremoved from groove 110.

In the embodiment of FIG. 7, grooves 11 are positioned adjacent oneanother along the entire terminal portion 12 of plug 10. In thisembodiment detents 60' and 60" are not positioned directly opposite oneanother, but rather are positioned so that catch 61" would engagebeveled end 13 slightly ahead of catch 61. Therefore, it is notnecessary that plug 10 be inserted for sufficient length to cause it tobe moved the entire distance between grooves before locking can againoccur. It is only necessary that it be moved approximately one-half thedistance between grooves for locking to again occur. While catch 61engages groove 1 1e catch 61" rests against the outer circumference 12between grooves lie and 11f. Continued insertion of plug 10 intoreceptacle l5 first causes catch 61" to move into groove 11f while catch61 moves on the outer circumference 12 of plug 10. Plug 10 then can bemoved only the slightest distance in either direction before finger 61or 61" engages one of its grooves and locks the plug against furthermovement in either direction, as long as the receptacle is energized.

I claim:

1. In an electrical receptacle and plug, the receptacle having a firstset of electrical contacts adapted to be energized by connection to apower source, the plug having a second set of electrical contactsadapted to be energized by connection to said power source through saidfirst set of contacts, the improvement comprising: a cylindrical collaron said plug, and receiving means for receiving said cylindrical collarinto said receptacle, said collar, receiving means, first set ofcontacts, and second set of contacts being constructed to requirepartial insertion of said collar into said receiving means before saidfirst and second set of contacts engage; said collar having a beveledend thereof and having circumferential grooves along its outermost wall,said receptacle having obstructing means for obstructing the path ofsaid cylindrical collar within said receiving means during said initialpartial insertion; resilient means for moving said obstructing meansinto the path of said collar; lock means for maintaining saidobstructing means in the path of said grooves,- said lock means beingpowered by current supplied to the lock means in parallel with the firstset of electrical contacts; whereby insertion of the cylindrical plug isprevented when the first set of contacts are energized, and whereby thewithdrawal of the plug to electrically disconnect the plug from thereceptacle is prevented while the first set of contacts are energized.

2. The combination of claim 1 in which the obstructing means comprises apivotable finger extendable inwardly from said receiving means into thepath of the cylindrical plug, spring means for urging the finger in thedirection of the plug, plunger means for obstructing the pivoting of thefinger out of the path of the plug, said plunger means including anobstruction portion and a shaft portion, said obstruction portion beingmovable into a first position which obstructs the pivoting of thefinger, and being movable to a second position which does not obstructthe pivoting of said finger; second spring means for urging the plungermeans to rest in the second position; solenoid means for moving saidplunger means to said first position whenever the first set ofelectrical contacts are energized, said solenoid means being energizedin parallel with the receptacle leads; whereby the finger is moved intothe path of the cylindrical plug by the first spring means and can bemoved out of the path of the cylindrical collar by insertion of saidcollar when said obstructing portion is in said first position, butcannot be moved out of the path of said collar when the solenoid isenergized and the obstructing portion is thereby moved to the secondposition; said plunger means being operatively engaged to said solenoidthrough said shaft portion, the shaft being urged towards the directionof the solenoid by the sealing of the solenoid, the shaft being urged ina direction away from the solenoid by second spring means.

3. The combination of claim 2 inwhich the plunger means includes anobstructing portion through which the shaft portion passes and includesmeans for sliding said obstructing portion on said shaft portion,whereby said shaft can move to seal the solenoid when the obstructingportion is restrained in its first position by the finger.

4. In an apparatus including a mating electrical receptacle member andplug member where the members have electrical contacts which interengagewhen the members are mated, said contacts extending longitudinally ofthe members, the members moving longitudinally when being mated or beingseparated, and means including a solenoid to lock the members togetherwhen electrical energy is present at the contacts of one member, theimprovement wherein said means comprises:

the other of said members having a portion adjacent the one member whenthe two members are at least partially mated, said portion of said othermember defining a plurality of abutment means positioned at intervalslongitudinally of said other member;

a detent moveably mounted on said one member for movement between afirst position at which it engages said abutment meahs and a secondposition at which it is free of said abutment means; resilient means onsaid one member and operatively associated with said detent toresiliently urge said detent toward said first position and away fromsaid second position; l

a locking bolt moveably mounted in said one member for movement betweena first bolt position at which the bolt blocks the movement of thedetent away from the first position thereof and,.a second bolt positionat which the detent is free to move away from its. first position and toits second position; and

bolt actuating means including said solenoid to move the bolt from itssecond bolt position and toward its first bolt position when saidsolenoid is energized and to its second bolt position when said solenoidis deenergized; whereby there are a plurality of positions of themembers. with respect to each other at which the members in onedirection with respect to each other will be blocked by the detent whenthe solenoid is energized.

5. In an apparatus as set forth'in claim 4, wherein the contactsincludes power contacts and control contacts with at least some of thepower contacts being longer than the control contacts so that the powercontacts engage before the control contacts when the members are movedtoward mating position, said plurality of abutment means including onepositioned to be engaged by said detent after the power contacts haveengaged but before the control contacts have engaged.

6. In an apparatus as set forth in claim 5, wherein said detentcomprises an arm pivotally connected to said one member, said bolt beingmounted for movement along a line longitudinally of said one member, andsaid solenoid has an armature axially aligned with said line.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,569,908 Dated March 197]- Inventor(s) Arthur I. A pleton It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 5, line 19, "grooves" should read collar-. Column 5, line 19,before the comma should be inserted --either at the end of the collar orin one of said groove Signed and sealed this 22nd day of June 1971.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

EDWARD I LFLE'I'CHHH, JR. Attesting Officer Commissioner of Patents

1. In an electrical receptacle and plug, the receptacle having a firstset of electrical contacts adapted to be energized by connection to apower source, the plug having a second set of electrical contactsadapted to be energized by connection to said power source through saidfirst set of contacts, the improvement comprising: a cylindrical collaron said plug, and receiving means for receiving said cylindrical collarinto said receptacle, said collar, receiving means, first set ofcontacts, and second set of contacts being constructed to requirepartial insertion of said collar into said receiving means before saidfirst and second set of contacts engage; said collar having a beveledend thereof and having circumferential grooves along its outermost wall,said receptacle having obstructing means for obstructing the path ofsaid cylindrical collar within said receiving means during said initialpartial insertion; resilient means for moving said obstructing meansinto the path of said collar; lock means for maintaining saidobstructing means in the path of said grooves, said lock means beingpowered by current supplied to the lock means in parallel with the firstset of electrical contacts; whereby insertion of the cylindrical plug isprevented when the first set of contacts are energized, and whereby thewithdrawal of the plug to electrically disconnect the plug from thereceptacle is prevented while the first set of contacts are energized.2. The combination of claim 1 in which the obstructing means comprises apivotable finger extendable inwardly from said receiving means into thepath of the cylindrical plug, spring means for urging the finger in thedirection of the plug, plunger means for obstructing the pivoting of thefinger out of the path of the plug, said plunger means including anobstruction portion and a shaft portion, said obstruction portion beingmovable into a first position which obstructs the pivoting of thefinger, and being movable to a second position which does not obstructthe pivoting of said finger; second spring means for urging the plungermeans to rest in the second position; solenoid means for moving saidplunger means to said first position whenever the first set ofelectrical contacts are energized, said solenoid means being energizedin parallel with the receptacle leads; whereby the finger is moved intothe path of the cylindrical plug by the first spring means and can bemoved out of the path of the cylindrical collar by insertion of saidcollar when said obstructing portion is in said first position, butcannot be moved out of the path of said collar when the solenoid isenergized and the obstructing portion is thereby moved to the secondposition; said plunger means being operatively engaged to said solenoidthrough said shaft portion, the shaft being urged towards the directionof the solenoid by the sealing of the solenoid, the shaft being urged ina direction away from the solenoid by second spring means.
 3. Thecombination of claim 2 in which the plunger means includes anobstructing portion through which the shaft portion passes and includesmeans for sliding said obstructing portion on said shaft portion,whereby said shaft can move to seal the solenoid when the obstructingportion is restrained in its first position by the finger.
 4. In anapparatus including a mating electrical receptacle member and plugmember where the members have electrical contacts which interengage whenthe members are mated, said contacts extending longitudinally of themembers, the members moving longitudinally when being mated or beingseparated, and means including a solenoid to lock the members togetherwhen electrical energy is present at the contacts of one member, theimprovement wherein said means comprises: the other of said membershaving a portion adjacent the one member when the two members are atleast partially mated, said portion of said other member defining aplurality of abutment means positioned at intervals longitudinally ofsaid other member; a detent moveably mounted on said one member formovement between a first position at which it engages said abutmentmeans and a second position at which it is free of said abutment means;resilient means on said one member and operatively associated with saiddetent to resiliently urge said detent toward said first position andaway from said second position; a locking bolt moveably mounted in saidone member for movement between a first bolt position at which the boltblocks the movement of the detent away from the first position thereofand a second bolt position at which the detent is free to move away fromits first position and to its second position; and bolt actuating meansincluding said solenoid to move the bolt from its second bolt positionand toward its first bolt position when said solenoid is energized andto its second bolt position when said solenoid is deenergized; wherebythere are a plurality of positions of the members with respect to eachother at which the members in one direction with respect to each otherwill be blocked by the detent when the solenoid is energized.
 5. In anapparatus as set forth in claim 4, wherein the contacts includes powercontacts and control contacts with at least some of the power contactsbeing longer than the control contacts so that the power contacts engagebefore the control contacts when the members are moved toward matingposition, said plurality of abutment means including one positioned tobe engaged by said detent after the power contacts have engaged butbefore the control contacts have engaged.
 6. In an apparatus as setforth in claim 5, wherein said detent comprises an arm pivotallyconnected to said one member, said bolt being mounted for movemEnt alonga line longitudinally of said one member, and said solenoid has anarmature axially aligned with said line.